Pro-autonomy Tuareg MNLA rebels said one of their patrolsseized Mohamed Moussa Ag Mohamed, an Islamist leader who imposedharsh sharia (Islamic law) in the desert town of Timbuktu, andOumeini Ould Baba Akhmed, thought to be responsible for thekidnapping of a French hostage by al Qaeda splinter group MUJWA.

"We chased an Islamist convoy close to the frontier andarrested the two men the day before yesterday," Ibrahim AgAssaleh, spokesman for the MNLA, told Reuters from Ouagadougouin Burkina Faso. "They have been questioned and sent to Kidal."

France has deployed nearly 4,000 ground troops, as well aswarplanes and armoured vehicles in its three-week-old OperationServal that has broken the Islamist militants' 10-month grip onnorthern towns. It is now due to gradually hand over to aU.N.-backed African force of some 8,000 troops, known as AFISMA,of which around 3,800 have already been deployed.

Paris and its international partners want to prevent theIslamists from using Mali's vast desert north as a base tolaunch attacks on neighbouring African countries and the West.

After meeting French President Francois Hollande in Paris,U.S. Vice President Joe Biden praised the "decisiveness andincredible competence" of France's operations. He backedFrance's call for U.N. peacekeepers to be deployed in Mali.

"We agreed on the need to, as quickly as reasonablypossible, establish an African-led mission to Mali and, asquickly as is prudent, transition that mission to the UnitedNations," Biden said, flanked by Hollande.

Paris believes that deploying U.N. peacekeepers to Malicould eliminate problems over funding the African mission andfears of ethnic reprisals by Malian troops against light-skinnedTuaregs and Arabs associated with the Islamists.

BAMAKO HESITATES OVER TALKS

The MNLA, which seized control of northern Mali last yearonly to be pushed aside by better-armed Islamist groups,regained control of its northern stronghold of Kidal last weekwhen Islamist fighters fled French air strikes into hideouts inthe nearby desert and rugged Adrar des Ifoghas mountains.

The Tuareg group says it is willing to help the French-ledmission by hunting down Islamists. It has offered to hold peacetalks with the government in a bid to heal wounds between Mali'srestive Saharan north and the black African-dominated south.

"Until there is a peace deal, we cannot hold nationalelections," Ag Assaleh said, referring to interim MalianPresident Dioncounda Traore's plan to hold polls on July 31.

Many in the southern capital Bamako - including army leaderswho blame the MNLA for executing some of their troops at theSaharan town of Aguelhoc last year - strongly reject any talks.

"One of the first conditions for reconciliation is to disarmrebel groups," Malian Foreign Minister Tieman Hubert Coulibalytold Reuters in Paris. "We must first liberate the north of Maliand then we can organise elections."

French special forces took the airport in Kidal on Tuesday,reaching the most northern city previously held by the Islamistalliance. The French presence at the airport has since beenreinforced by two parachute units.

Though the MNLA says it controls Kidal, France's defenceministry said on Monday that 1,800 Chadian troops - part of aU.N.-backed African mission sent to help retake northern Mali -had entered the city.

TARGETING REBEL BASES, DEPOTS

French Foreign Minister Laurent Fabius said warplanes werecontinuing bombing raids on Islamists in Mali's far north todestroy their supply lines and flush them out of remote areas.

"The objective is to destroy their support bases, theirdepots because they have taken refuge in the north and northeastof the country and can only stay there in the long-term if theyhave the means to sustain themselves," Fabius said.

"The army is working to stop that," he told French radio.

Jets attacked rebel camps on Sunday targeting logisticsbases and training camps used by the al Qaeda-linked rebels nearTessalit, a town close to the Algerian border.

In all, French jets and attack helicopters have hit 25targets in Kidal and areas surrounding Aguelhok and Tessalitsince Friday, the defence ministry said.

Hollande made a one-day trip to Mali on Saturday, promisingto keep troops in the country until the job of restoringgovernment control in the Sahel state was finished. He waswelcomed as a saviour by cheering Malians.